class Type:
    pass



class SequenceType(Type):
    def __init__(self,subtypes):
        self.subtypes = subtypes

    def __repr__(self):
        return "[" + ", ".join(map(str,self.subtypes)) + "]"

class PitchType(Type):
    def __repr__(self):
        return "Pitch"

class DurationType(Type):
    def __repr__(self):
        return "Duration"
